Calling function from within same module it's declared is undefined/is not available

Questions / Help
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1

Redoing this to be more clear:

Question

How can I call a function inside a module?

File: test.exs

defmodule MyModule do

  def sum(a, b) do
    a + b
  end

  MyModule.sum(1,1) # or sum(1,1)
end

elixir test.exs :

** (UndefinedFunctionError) function MyModule.sum2/2 is undefined (function not available)
    MyModule.sum2(1, 1)

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Original question asking same thing but more confused:
This is an .exs file used for Phoenix migrations, so it’s inside the folder /priv/repo/migrations. (In case that matters). I wrote a function but it’s totally blocked. I don’t want to import it from another module since this is where it goes (declared and used in same module)


defmodule MyApp.Repo.Migrations.MyModule do
  use Ecto.Migration

  def sum1(a, b) do #public
    a + b
  end
 defp sum2(a, b) do #private
    a + b
  end

end

From iex -S mix

iex(2)> MyApp.Repo.Migrations.MyModule
MyApp.Repo.Migrations.MyModule

iex(3)> MyApp.Repo.Migrations.MyModule.sum2
** (UndefinedFunctionError) function MyApp.Repo.Migrations.MyModule.sum2/0 is undefined (module MyApp.Repo.Migrations.MyModule is not available)
    MyApp.Repo.Migrations.MyModule.sum2()


iex(4)> MyApp.Repo.Migrations.MyModule.sum1(1,1)
** (UndefinedFunctionError) function MyApp.Repo.Migrations.MyModule.sum1/2 is undefined (module MyApp.Repo.Migrations.MyModule is not available)
    MyApp.Repo.Migrations.MyModule.sum1(1, 1)
    iex:4: (file)

If U can’t call it like this, this is what I want to do. It gives the same error as the above attempt.

defmodule MyApp.Repo.Migrations.MyModule do
  use Ecto.Migration

  def sum1(a, b) do
    a + b
  end
 defp sum2(a, b) do
    a + b
  end
IO.puts(sum1(1,1)) #or sum2(1,1)
end

Pls Ignore it being bad practice (if it is) to have a function in a migration file, unless this the cause.

Real use case (Not sure if this link is accessible to all?)

2

In iex you have not loaded the migration module. You’ve just defined the module name as an atom. Since it’s a .exs instead of .ex it is not compiled and loaded automatically with iex -S mix

1 Like
3

Also, both of your functions aren’t exported, so you cannot call them outside of the module.

4

If I run the migrarions ecto.migrate I immediately get

(CompileError) priv/repo/migrations/20230227174711_MyModule.exs:26: undefined function sum2/2 (there is no such import).

Same for sum1

That is with this line inside the module IO.print(sum2(1,2))

Shouldn’t this solve that issue?

5

Don’t know to export functions. Looking that up. Link to examples possible? :slight_smile:

Also, see the case where the function is called inside the module. I get the same error for both cases.

6

In Elixir? Just use def instead of defp.

7

Sorry I had a typo. One is public, one is private - only for example here. I don’t have it as private in practice.

Makes no difference here. Get same error

I see what U mean, that that is required to export. But I’m trying to call within the same module. I’m not trying to do anything at all fancy - just write a function and call it.

8

This may really be an XY Problem. Are you familiar with mix run? It lets you run an Elixir function from the command line.

9

If I call mix run /priv/repo/migrations/my_module.exs I get undefined function sum/2 (there is no such import)

I’m not sure I’ll be able to call the file like this anyway, since it’s a phoenix file? Still, error is still the same error.

I’ll try moving the function out to another file. If u see the replit link I added this is not specific to phoenix or migrations (just calling a function inside a module - the real question), and it still causes the error.

It might make U login to this though, not sure.

10

Deleted reply

11

Replace this with:

defmodule MyModule do
  def sum(a, b) do
    a + b
  end
end

MyModule.sum(1,1)

Namely call it outside of the module, not inside of it. When you are trying to run code inside the module body – but NOT inside a function body – then you are effectively trying to run code that wasn’t compiled yet (if I remember correctly).

So if your goal is to define a module with functions and then immediately call them, my above code is a good way to do it.

1 Like